The Langkilde Lab in Action

Tag Archives: Fire ant

I’ve certainly attracted my share of unwanted attention: missing a key free throw in a basketball game when everyone in the crowd was watching, faceplanting while exiting stage right in A Midsummer Night’s Dream, or unconsciously ripping a huge burp at a fancy dinner. Fortunately, as a human, the stakes involved in these mistakes were fairly low: a little embarrassment and a good story once the shame had worn off. For many organisms, like lizards, however, attracting unwanted attention in the real world can have serious consequences…

From previous research in the Langkilde Lab, we know that invasive fire ants (Solenopsis invicta) can pose a serious danger to native fence lizards (Sceloporus undulatus), and that fence lizards from areas invaded by fire ants respond to encounters with these ants with a variety of twitches and scratches to remove ants as well as fleeing more often to escape them.

We know little, however, about the behavioral rules that govern fleeing and twitching in these lizards. Do they flee more from all predators? Do they flee from all ants? We know the benefit of twitching and fleeing (not getting stung!), but is there any cost to these behaviors? Because we’re ecologists, we looked to answer these questions by conducting a series of experiments and published them in Animal Behaviour.

So, do fence lizards from fire ant-invaded areas flee more from other predators? Because we couldn’t let actual predators attack our lizards, I borrowed a stuffed kestrel (Falco sparverius, a well-known predator of fence lizards), rigged it with a wire harness, attached some very serious and scary-looking eyes, and swung it at unprepared fence lizards to see what their reactions would be.

Taxidermied kestrels are mostly as scary as the real thing.

We found that fence lizards from sites with and without fire ants fled from simulated kestrel attacks the same proportion of the time, and with the same strength and latency (reaction time), suggesting that fence lizards exposed to fire ants don’t flee more from all predators.

We next tested our fence lizards’ reactions to fire ants (which we’ve done before) as well as two types of native ants which might annoy lizards by running on them, but lack the venom (and danger) of fire ants. In fact, these native ants are important sources of food for fence lizards under normal circumstances. In these tests, we found that fence lizards from sites with fire ants fled more from all types of ants, not just fire ants, indicating that this fleeing behavior is generalized to multiple types of ants that they encounter, including those that don’t pose a serious danger.

For the more visually oriented, this series of experiments was illustrated super-well by Tali Hammond, a behavioral ecologist, who was interested in the paper (check out that sweet Sceloporus!)

So what might the consequences of this generalization be for fence lizards? For one, it’s obviously not ideal to be running away from something (i.e., native ants) that isn’t a threat and should be a meal. This could result in lower food intake or time wasted running away from non-dangerous ants, though we haven’t tested for these effects. More dramatically, twitching and fleeing break crypsis, a lizard’s primary defense against its visually hunting predators, including snakes, and birds of prey like the kestrel. While fence lizards are usually quite well camouflaged, imagine how easy it might be for a predator to spot a lizard jerking around as in the video above. We looked for evidence of this cost in our lizards by quantifying the amount of injuries (broken tails, scars, missing limbs) to lizards at sites with and without fire ants.

A missing “hand” is an example of injuries many fence lizards have.

We found that lizards from sites with fire ants do indeed have more of these injuries than lizards at sites without fire ants. This result suggests that fleeing from fire ants might attract unwanted attention from other types of predators. And when we consider that these lizards also flee more from native ants, which are common in the environment, these antipredator behaviors might have a serious drawback. It is important to note that this evidence is circumstantial; we didn’t see predators preying on lizards running from ants (this would be very difficult), and there could be other explanations for this pattern, such as differences in predator communities, or perhaps differing skill levels of predators. However, this work suggests that lizard that twitch and flee in response to ants may be attacked more.

So why do we see this behavior if it has these drawbacks? My personal guess is that it comes down to consequences. As a human, the consequences of my unwanted attention were fairly minor (shame). The stakes for fence lizards are a bit higher: fleeing can lead to running from your own dinner or attracting attention from predators. BUT the costs of not fleeing when attacked by fire ants are likely even higher (serious injury or death). And in many areas fire ants are much more common and likely to interact with lizards more frequently than snakes and kestrels. In other words, the lizards are likely making the best choice available to them. In the future, perhaps, they will adapt to distinguish between dangerous and native ants, allowing them to make more optimal decisions, and reduce the costs of these antipredator behaviors. More broadly speaking, I believe this research shows that we need to consider a wide variety of potential costs as well as benefits when looking at organisms adapting to changes in their environments.

Even though I am continuing the same project from last year (how maternal stress affects the offspring in fence lizards), there are still some striking differences. One of the biggest is that there are fellow grad students and a post doc this summer!

From left to right: Cameron (PhD), myself (PhD), Kirsty (post-doc), and Dustin (PhD).

Also, last year we made the drive in one day, however this year we broke the drive up over 2 days. This gave us an excellent opportunity to experience different parts of the USA on our drive. For the night we stopped in Knoxville, TN and had dinner at an amazing place called Calhoun’s On The River. True to its namesake, it had a beautiful view of the Tennessee River!

After all the driving, we finally made it back to Solon Dixon and started catching lizards. As usual, the lizards’ personalities were very evident.

Male fence lizard unamused with our attempts to catch him

Apparently the female lizards found that corner of the tub to be very interesting.

As I went to put this female back in her tub, she refused to let go of my fingers!

On top of finding many fence lizards, we were also about to see many other reptiles and amphibians!

A barking tree frog tightly hugging my finger.

An American alligator, at a very reasonable size to handle.

A yellow bellied slider who found a little bit of water to sit in.

A glass lizard!

As I spend more time down here, I find it rubbing off on me more and more.

Very tempted to get a cowboy hat.

After catching the females, our first trip came to an end. However, we were quickly back down to release the females and run experiments with the hatchlings. With us this time we had an undergraduate researcher, Jen!

The Bayfront Park, overlooking Mobile Bay. Located right next to one of our field sites, Blakeley State Park.

As we wait for more hatchlings to emerge, we have been focusing on removing fire ants from some of the enclosures we built. As fire ants are highest in the mounds earlier in the day, this means some early mornings. On the up side, it also means we always get to see the sunrise.

Sunrise right near the enclosures.

Most things have gone well, with only one piece of equipment starting to show signs of wear, but this just gave me an excuse to do some handywork!

Used some steel epoxy to seal a leak in the pot we boil water in for fire ants.

Things have started to pick up in terms of hatchling, so soon you should be able to hear about how things are going with them. Until then, here is a pic from right here at Solon Dixon

Since joining the lab, I’ve heard nothing else more than field seasons in Alabama; from the heat, lizards, those darn fire ants, and the wonderful people they come in contact with. So of course, I was anxious as ever to finally embark on my first field season in the Langkilde lab. After months of preparation, designing projects and all the logistics involved, May 9th had finally arrived and it was time to head south.

The first round of people in the Alabama crew this year had 3 newbies to the lab; Dustin Owen (our personal herpetology specialist), Dr. Kirsty Macleod (our Scottish Post Doc who should’ve been born in the southern US) and Myself aka Frog stallion (long story). The last member of the crew was David Ensminger. This was his third year there, sort of making him our expert of all things and everything that we needed to know (in other words he was our ear to ask a million questions).

The wonderful staff of The Solon Dixon Forestry Education Center welcomed us to the 5 starred field station (in my opinion – I don’t know who could possibly refute that). There were also lots of Auburn University students that were super interested in our work and simply cool people to hang out with. Essentially, everyone we met made sure we left knowing that southern hospitality is 100% real. I now understand why everyone in the lab loves and talks about it so much.

Some Auburn students were successful on their first lizard hunt. It was Herp week in their class, luckily for them, they had some experienced catchers around

Now on to the fun science! In case you’re reading this and don’t know, the Langkilde lab is well invested into the Fence Lizard and Fire Ant system, but I’m just going to focus on my specific part for now. In the broadest of terms, I am interested in the diet of the Fence Lizards, but of course I can’t help but wonder about other aspects of this creature. A former member of our lab (the undergrad king Mark Herr) published a paper that suggests fence lizards seemingly build an addiction to the fire ants. My first thought was the possibility that the fire ants may be more nutritious. In Alabama, I collected loads of ants to quantify carbs, lipids, and proteins in comparison to fire ants, hoping for something to support a risk-reward relationship. My next thought was, if the lizards are presented with a second option, what will they pick? To test this, The Lizard Queen (Dr. Tracy Langkilde) and I ran food preference trials. We used the fire ants and “Dory ants” (still waiting for a true identification, but we call them Dory ants) in tubs with one lizard to see the choices they made. Now back in State College, I’m going through and analyzing all the data. I won’t spoil the surprise, which will hopefully be published, so stay tuned in the near future.

My first Catch of the trip. Gotta love when they just pose and hug your thumb!

Short answer: Nope. Fire ants like their lizard eggs raw. Our recently accepted paper in the Journal of Herpetology “Invasive Fire Ant (Solenopsis invicta) Predation of Eastern Fence Lizard (Sceloporus undulatus) eggs” shows that fire ants do indeed eat fence lizard eggs in a natural setting, but, despite being known as “fire” ants, these hymenopterans haven’t quite mastered the art of cooking their food prior to chowing down. Get your non-final, still with a couple of mistakes, pre-print copy online (paywalled) or download one from this blog (posted for personal use of our readers courtesy of SSAR)!

At this point, you may be asking yourself, “Why should I care if fire ants eat fence lizard eggs?”, so I’ll discuss the impetus behind this project. Previous research in the lab had given us a good idea of how fire ants can impact juvenile and adult fence lizards: they are found frequently on the ground by fire ants, stung if they don’t run away, and can be envenomated when eating fire ants. BUT we knew incredibly little about what impacts fire ants might have on one unexplored life stage of fence lizards: eggs! And unlike juveniles and adults, these eggs can’t flee or twitch when attacked by fire ants; they remain in a nest for 55-70 days (depending on site and temperature), during which time they might be vulnerable to fire ants. Additionally, fence lizards often (though not always) prefer sandy sites with low canopy cover, where sunlight can warm the nest, exactly the type of microhabitat beloved by fire ants. And fence lizards build their nests 4-8 cm underground, right at the same depths where fire ants construct their underground foraging tunnels. We surmised that fire ants might come into contact with fence lizard eggs with some frequency, and, if fire ants ate the eggs, this might have a large impact on fence lizard populations.

Fire ants are known to eat the eggs of other reptiles, including those of snakes, turtles, and some lizards (such as anoles). To determine if fire ants were physically capable of eating fence lizard eggs, Jill Newman (a former lab undergrad who just started her master’s at Clemson…wooooooo!), Tracy, and I designed a small experiment. We presented fence lizard eggs to captive fire ant colonies and observed them penetrate the eggs in less than 30 minutes…a rather dramatic response! However, we also wanted to see whether fire ants might eat fence lizard eggs under more natural conditions. To address this, Jill dug holes in the ground to the depth of fence lizard nests and placed 12 eggs near fire ant mounds overnight. Upon examination, 11 of the 12 eggs had been punctured and eaten in less than a day!

The next summer, I designed a follow-up experiment to learn more about this type of predation. Specifically, I wanted to know how many eggs fire ants might eat, how quickly they might find them, and whether any environmental variables, like distance of a fence lizard nest from a fire ant mound, might affect predation. To address this, I started by collecting fence lizard eggs. A LOT of fence lizard eggs (over 150!…I resisted the urge to make my own omelet).

I couldn’t, however, just bury the eggs in the ground and check them after 24 hours (as Jill did) to answer my question about how long eggs might survive…I had to be (a little) creative. After reading about a similar problem faced by Kurt Buhlmann and his solution when he wanted to monitor turtle eggs, I developed a method allowing me to monitor the eggs daily without disturbing them (which might attract fire ants and increase predation).

For each nest, I dug a hole into the ground and sunk into it a clear, capped acrylic tube. I carefully replaced the sandy soil around each tube and placed six eggs (a small, but reasonable size for a fence lizard nest) next to the tube. I inserted a small piece of plastic transparency above the eggs and then carefully covered the whole arrangement with the soil. The transparency prevented soil from entering between the eggs and the acrylic tube, and, by lowering a video camera into the tube, I could count the eggs and see if they were being attacked by ants (or other predators). At each “nest” I also measured the amount of canopy cover and the distance to the nearest fire ant mound.

Diagram of nest tube with camera for viewing eggs underground.

…aaaaand what one of them looks like in the ground.

Each day, for up to 20 days, I monitored the nests and recorded if all the eggs were present. If I found ants attacking the eggs, I waited a few hours to let them eat the eggs (or at least let them make a start) and then dug up the nest to catch and identify some of the ants. I can definitively say that fire ants do not like to be disturbed when they are in the middle of a meal! Because of our innovative setup, it only took about 3 minutes a day to monitor each nest (check out a couple of examples below).

In our trials, we found that 24% of nests were attacked by fire ants within 20 days. Extrapolating this to the full incubation period of fence lizards using a mathematical model, we estimated that up to 61% of fence lizard nests are in danger of being preyed on by fire ants. We also did not find any relationship between how far nests were from fire ant mounds and how likely they were to be eaten. Given the high densities of fire ants at many areas in the Southeast, it seems likely that fire ants prey on a substantial portion of fence lizard nests in the wild. Of course, we know that fence lizard populations where we do our research are not in danger of disappearing. Fence lizards are doing fine even in the face of this predation, which is great news, and suggests that survival in other parts of a fence lizard’s life or high reproductive output may allow them to persist in fire ant invaded areas. In the future, I am aiming to build mathematical population models to understand the impacts of egg predation by fire ants, and see how this predation may affect populations over the long term.

One other point of note is that, for many species of southeastern herps that are declining, such as kingsnakes or southern hognose snakes, fire ants are often suggested as a culprit without any definitive proof. My project suggests that fire ants can indeed prey on large portions of the nests of some species, but also shows that one species is doing just fine even when fire ants may be making a buffet of about half of its nests. Moving forward, I would recommend that lab and field trials like those we’ve done be used to pinpoint if fire ants are indeed a threat to the eggs of these other species, and, if so, what proportion of nests are at risk.

Where do I begin? I guess I will start with a little background info. My name is Cameron Venable and I hail from the great state of Maryland. If that means nothing to you, then in a nutshell I really love the MD flag and crabs (which is a key part of a Marylander’s life). Anyway, after high school, I went to Lebanon Valley College in Annville, PA. At LVC I majored in Biology and minored in Spanish. As a side-note of my story, LVC was around 1500-1600 people… TOTAL. So coming to PSU was a huge jump! Not only were there exponentially more people, but also grad school is a completely different world.

I may be the odd ball of the current students because I am a second year. So how am I just now introducing myself? Well, that’s another long story, but basically I switched advisors last semester and joined the Langkilde Lab (for my lab-mates that may read this, thanks for making me feel welcomed). As a part of this lab, I’ve been endlessly brainstorming for future projects to begin. As of now the big plans for the near future are as follows:

1) Embryo nutrition in the fence lizard and fire ant system. The idea would be to investigate the influence of fire ant presence on the maternal input into offspring.

2) Looking forward to working with a past member of the Lab, Dr. Lindsey Swierk within her study system, which will focus on how urbanization affects wood frogs in various ways.

3) Lastly, becoming an expert on Bomb Calorimetry, which would be helpful for various projects in quantifying nutrition.

Those are the ideas for the upcoming months, but of course in this field things are subject to change. Which means… Stay tuned for the adventure!!!

2015 ended in style for the Langkilde Lab, and we are proud to report that thus far 2016 has been just as exciting! In the last few months, we have celebrated a number of lab accomplishments and enjoyed some attention from the media. Here’s a taste of what we have been celebrating:

Press:

Penn State News featured the lab’s work on adaptation to invasive species and anthropogenic noise in this great article by Matt Swayne, complete with disco references. It’s definitely worth the read!

Penn State Science recently covered the lab’s research on the effects of stress, our collaborations, and Tracy’s mentoring style. The story quotes many lab members and also includes a “person-to-person” feature on graduate student Gail McCormick.

Other achievements:

PI Tracy Langkilde recently accepted the position as the Head of the Department of Biology.

Gail McCormick successfully defended her PhD dissertation and won the Alumni Association Dissertation Award. This award is among the most prestigious available to Penn State graduate students and recognizes outstanding achievement in scholarship and professional accomplishment.

Chris Thawley won the Intercollege Graduate Student Outreach Award, a university-level award that recognizes outstanding achievements related to bringing scholarship to the community. Chris will be defending in February and will be starting a post-doc with the Kolbe Lab in May, where he will be investigating the effects of urban light on anoles.

Kirsty MacLeod will be joining the Langkilde and Sheriff Labs as a post doc this spring. We are excited to have her!

Michaleia Mead will be staying on as a Masters student with Chris Howey. They will be investigating the effects of prescribed burns on amphibians and vernal pools.

Hooray!

Stay tuned throughout 2016 for more exciting research and updates from the Langkilde Lab!

Hello, my name is Dustin Owen and I’m one of three new PhD students in Tracy Langkilde’s Lab. I’m originally from east-central Indiana where I got my B.S degree in Biology from Ball State University. While there I was able to work on a lot of different questions on a lot of different organisms. My first research project was on the allometry of shell morphology in a freshwater snail,Elimia livescens, in Dr. Mark Pyron‘s Lab. After that I worked on several other projects including looking at hydrology and freshwater drum (Aplodinotus grunniens) with Dr. Pyron, artificial scent and small mammal trapping and various bat projects with Dr. Timothy Carter, and even my own independent research project on how roads impact the stress physiology of copperheads (Agkistrodon contortrix).

Copperhead (Agkistrodon contortrix) on a gravel road.

After my undergrad, I went to Austin Peay State University and continued my interest in stress physiology and reptiles. While there, I studied stress physiology in several species of snakes.

Racer (Coluber constrictor) Selfie

Now that I’m here at Penn State I plan on continuing my interest in stress physiology, using the invasive Fire Ant (Solenopsis invicta) and Eastern Fence Lizard (Sceloporus undulatus). While I have never directly studied Fence Lizards in the past, I have assisted expert Fence Lizard catcher Kris Wild on his Master’s Thesis work on fire and Fence Lizards. Now, armed with my new Kris Wild custom lizard noose, “The Pub Maker”, I’m ready to lay siege to some fence lizards in the name of science!

In my spare time I enjoy being outside, football, basketball, and hanging out with my girlfriend Heather. I also enjoy exploring with my niece Lilly. Teaching her about biology (she’s especially interested in bats and snakes) has been one of the greatest joys in my life. One day, she’ll be a far greater biologist than I’ll ever be, but until then I’m happy just taking her outside and watching her learn about nature.

Me with a juvenile Common Water Snake (Nerodia sipedon) and Lilly with a Ring-necked Snake (Diadophis punctatus).